Relief device for oil circuit of engine

ABSTRACT

A relief device including: an oil pump; an upstream flow passage provided from a discharge section side of the oil pump to an engine; an oil-pressure relief valve relieving oil by a valve body moving due to oil pressure; and a temperature-sensitive relief valve B relieving oil by detecting an oil temperature and opening and closing steplessly. The oil-pressure relief valve and the temperature-sensitive relief valve are disposed in parallel in the upstream flow passage. A portion of the pump housing of the oil pump is formed in an integrated fashion with a casing of an oil circulation mechanism. An oil filter  102  is provided in the upstream flow passage  61 , and the temperature-sensitive relief valve B is positioned on the upstream side of the oil filter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a relief device for an oil circuit of an engine, which is provided with an oil-pressure relief valve and a temperature-sensitive relief valve, whereby oil can be relieved (expelled) at a desired oil pressure, regardless of the oil temperature, and which has a simplified configuration.

2. Description of the Related Art

Conventionally, there is a variety of pumps for supplying oil for lubricating and cooling an engine, which are provided with a relief valve that relieves oil when the discharge pressure-exceeds a prescribed value. Moreover, there is also a relief device for an oil circuit of an engine, wherein it is determined whether or not to relieve oil in accordance with change in the temperature of the oil, as well as pressure change.

The third embodiment of Japanese Patent Application Publication No. 2006-214286 is a concrete example of a device of this type. The third embodiment of Japanese Patent Application Publication No. 2006-214286 is an oil pump provided with a first control valve (4) and a second control valve (7). A brief description of Japanese Patent Application Publication No. 2006-214286 is given here. The reference numerals used in Japanese Patent Application Publication No. 2006-214286 are used without modification here. The first control valve (4) is configured so as to function as a relief valve when the discharge pressure of the operating oil is high in a discharge oil passage (5) downstream of an oil pump X.

The second control valve (7) is a valve which controls the first control valve (4) and operates in accordance with the temperature of the operating oil, more specifically, which controls the pressure of the operating oil flowing into the second valve chamber (44) of the first control valve (4). The second control valve (7) is provided with a valve body operating mechanism (73) which causes the valve body (72) to perform a reciprocating action in accordance with the temperature of the operating oil. The valve body operating mechanism (73) is a temperature-sensitive expanding and contracting body (73 a) which expands and contracts, and more specifically, uses a spring made of shape-memory alloy.

The first control valve (4) and the second control valve (7) are connected by a first valve-to-valve oil passage (91) and a second valve-to-valve oil passage (92). The oil pressure in the valve body (42) of the first control valve (4) is controlled by switching between communication and non-communication of the first valve-to-valve oil passage (91) and the second valve-to-valve oil passage (92). In this way, in Japanese Patent Application Publication No. 2006-214286, the first control valve (4) and the second control valve (7) operate in a mutually coordinated manner, rather than operating independently.

SUMMARY OF THE INVENTION

In Japanese Patent Application Publication No. 2006-214286, the second control valve (7) expands and contracts in accordance with change in the oil temperature, and therefore the operation of the first control valve (4) is affected by the oil temperature. A high temperature means an oil temperature of approximately 110° C. to 130° C., for example, when the oil temperature is 50° C., then the oil viscosity becomes higher and therefore the oil pressure becomes higher, compared to when the oil temperature is approximately 110° C. to 130° C.

Therefore, when the oil is at low temperature, such as 50° C., the discharge pressure per revolution of the rotor is higher than when the oil temperature is approximately 110° C. to 130° C., and therefore the gradient of the straight line L1 shown in the drawings is steep, and the first control valve (4) relieves the discharge pressure when the discharge pressure has risen to a certain prescribed value. By means of the operation described above, since the oil pressure is higher when the oil temperature is lower, then there is large energy loss and this obstructs improvement in fuel consumption at low temperature.

The second control valve (7), which is a temperature-sensitive valve, is a control valve for increasing and reducing the relief pressure of the first control valve (4), and due to the serial connection, control variations in the second control valve (7) and control variations in the first control valve (4) are added together, giving rise to a large control variation. Furthermore, since the second control valve (7) is a valve which controls the oil pressure, rather than the flow volume, then it is a so-called on/off valve which transmits virtually all of the oil pressure when communicating to any extent, and therefore detailed control of the valve is difficult.

Therefore, the object of the present invention (the problem to be solved by the present invention) is to provide an inexpensive and highly reliable relief device for an oil circuit of an engine, whereby substantially the same oil pressure characteristics can be achieved irrespective of the oil temperature, and in particular, decline in fuel consumption at low temperature can be suppressed, by means of a very simple composition.

The inventors, as a result of repeated thorough research aimed at resolving the abovementioned problem, resolved the problem by configuring a first embodiment of the present invention to be a relief device for an oil circuit of an engine, the device including: an oil pump; an upstream flow passage provided from a discharge section side of the oil pump to the engine; an oil-pressure relief valve which relieves oil by a valve body moving due to oil pressure; and a temperature-sensitive relief valve which relieves oil by detecting an oil temperature and opening and closing steplessly, wherein the oil-pressure relief valve and the temperature-sensitive relief valve are disposed in parallel arrangement in the upstream flow passage, an oil filter is provided in the upstream flow passage, and the temperature-sensitive relief valve is positioned on the upstream side of the oil filter.

The inventors resolved the abovementioned problem by configuring a second embodiment of the present invention as the relief device for an oil circuit of an engine according to the first embodiment, wherein, when the oil temperature is low, the temperature-sensitive relief valve relieves oil. The inventors resolved the abovementioned problem by configuring a third embodiment of the present invention as the relief device according to the first embodiment, wherein, when the oil temperature is medium, the amount of oil relieved by the temperature-sensitive relief valve becomes greater near a low oil temperature, and becomes smaller near a high oil temperature. The inventors resolved the abovementioned problem by configuring a fourth embodiment of the present invention as the relief device according to the first embodiment, wherein, when the oil temperature is high, the temperature-sensitive relief valve does not relieve oil.

The inventors resolved the abovementioned problem by configuring a fifth embodiment of the present invention as the relief device for an oil circuit of an engine according to the first or second embodiment, wherein the temperature-sensitive relief valve is provided in the engine. The inventors resolved the abovementioned problem by configuring a sixth embodiment of the present invention as the relief device for an oil circuit of the engine according to the first or second embodiment, wherein a relief flow passage branches from the upstream flow passage, the oil-pressure relief valve and the temperature-sensitive relief valve are provided in a parallel arrangement, and the branch section of the relief flow passage is positioned to the upstream side of the oil filter.

In the present invention, by adopting a configuration wherein an oil-pressure relief valve which relieves oil by a valve body moving due to oil pressure, and a temperature-sensitive relief valve which opens and closes by detecting the oil temperature, are arranged in parallel, in an upstream flow passage provided from a discharge section of an oil pump to an engine or the main gallery of an engine, the oil-pressure relief valve and the temperature-sensitive relief valve operate in a mutually independent fashion.

In other words, the oil-pressure relief valve determines whether or not to perform an oil relieving operation by detecting the discharge pressure of the oil pump, and the temperature-sensitive relief valve determines whether or not to perform an oil relieving operation by detecting the oil temperature. Consequently, when oil is sent to the engine from the oil pump and via the upstream flow passage, the oil-pressure relief valve operates in response to change in the discharge pressure of the oil pump which may occur from a low number of revolutions to a high number of revolutions of the engine, and the temperature-sensitive relief valve operates in response to change in the oil temperature.

The oil-pressure relief valve and the temperature-sensitive relief valve are disposed in parallel arrangement inside the upstream flow passage, and each perform a relief operation either independently or simultaneously. Therefore, if either one of the oil discharge pressure from the oil pump and the oil temperature changes, and relieving of the oil becomes necessary, then oil can be relieved by either the oil-pressure relief valve or the temperature-sensitive relief valve, accordingly.

Here, parallel arrangement means that the oil-pressure relief valve and the temperature-sensitive relief valve are disposed so as not to be connected in series, and provided that the valves are disposed in parallel branches from the upstream flow passage, then parallel arrangement also includes configurations where one of the relief valves is disposed relatively nearer to the upstream side and the other of the relief valves is disposed relatively nearer to the downstream side.

In the configuration of the present invention, since the temperature-sensitive relief valve and the oil-pressure relief valve are connected in parallel, then the control variations of the respective relief valves are not added together, and hence more accurate control is possible. Furthermore, since the temperature-sensitive relief valve has a function of relieving oil by opening and closing steplessly, by detecting the oil temperature, then the temperature-sensitive relief valve is a valve that can be opened and closed steplessly, rather than a so-called on/off type of valve as in the prior art. For example, if the temperature-sensitive relief valve is opened a little, then a small amount of oil only is relieved, and therefore, the oil pressure is reduced only a little, and hence the oil pressure can be adjusted steplessly by adjusting the amount of opening/closing of the temperature-sensitive relief valve. Furthermore, by adopting a configuration wherein an oil filter is provided in the upstream flow passage and the temperature-sensitive relief valve is positioned to the upstream side of the oil filter, the temperature-sensitive relief valve can control the relieving of oil with sufficiently high accuracy, without being affected by differences in the pressure loss in the oil filter due to differences in the oil temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawings showing a configuration of an oil circulation circuit of an engine having a relief flow passage according to a first embodiment of the present invention;

FIG. 2 is an enlarged schematic drawing showing an oil relieving operation at a low oil temperature and a low number of revolutions of the engine;

FIG. 3 is an enlarged schematic drawing showing an oil relieving operation at a low oil temperature and a medium to high number of revolutions of the engine;

FIG. 4A is an enlarged schematic drawing showing an oil relieving operation near a low temperature in the medium temperature range and at a low number of revolutions of the engine; and FIG. 4B is an enlarged schematic drawing showing an oil relieving operation near a high temperature in the medium temperature range and at a low number of revolutions of the engine;

FIG. 5A is an enlarged schematic drawing showing an oil relieving operation near a low temperature in the medium temperature range and at a medium to high number of revolutions of the engine; and FIG. 5B is an enlarged schematic drawing showing an oil relieving operation near a high temperature in the medium temperature range and at a medium to high number of revolutions of the engine;

FIG. 6 is an enlarged schematic drawing showing an oil relieving operation at a high oil temperature and a low number of revolutions of the engine;

FIG. 7 is an enlarged schematic drawing showing an oil relieving operation at a high oil temperature and a medium to high number of revolutions of the engine;

FIG. 8 is a schematic drawings showing a configuration of an oil circulation circuit of an engine having a relief flow passage according to a second embodiment of the present invention; and

FIG. 9 is a graph showing the characteristics of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of this invention are described here with reference to the drawings. The present invention mainly includes: an oil-pressure relief valve A, a temperature-sensitive relief valve B, an oil circulation circuit 6, an upstream flow passage 61, a downstream flow passage 62 and an oil pump 9 (see FIG. 1 and FIG. 8). The oil-pressure relief valve A performs a relief (expelling) operation, in accordance with the discharge pressure from the oil pump 9. The oil-pressure relief valve A is configured by a valve body 1, an elastic member 2, and a valve housing 3 (see FIG. 1 and FIG. 8).

The valve body 1 is configured by a cylindrical small-diameter section 11, and a large-diameter section 12, which are coaxial and formed in an integrated fashion in the axial direction. The small-diameter section 11 is formed to a long dimension in the axial direction so as to form a substantially round bar shape, and the large-diameter section 12 is formed in a flat cylindrical shape. The end surface of the small-diameter section 11 at one end in the axial direction (the upper end surface of the valve body 1 in FIG. 1) is a pressure receiving surface 11 a.

A cylindrical projection section 14 is formed on the other end of the large-diameter section 12 in the axial direction (the lower surface end of the valve body 1 in FIG. 1). The projection section 14 serves to support the elastic member 2, such as the coil spring, and is structured so as to be inserted inside the elastic member 2, which is a coil spring.

The valve housing 3 is configured by a small-diameter valve chamber 31 and a large-diameter valve chamber 32. The small-diameter valve chamber 31 is a valve chamber in which the small-diameter section 11 of the valve body 1 performs sliding movement, and the large-diameter valve chamber 32 is a valve chamber in which the large-diameter section 12 performs sliding movement. In the small-diameter valve chamber 31, only the small-diameter section 11 performs sliding movement, but in the large-diameter valve chamber 32, the small-diameter section 11 is also inserted together with the large-diameter section 12.

A first relief inflow section 33 is formed in an end portion of the small-diameter valve chamber 31 of the valve housing 3 in the axial direction of the small-diameter valve chamber 31 (at the upper end of the valve housing 3 in FIG. 1). The first relief inflow section 33 is disposed between the valve housing 3 and the head portion of the valve body 1, and serves to allow oil to flow into the oil-pressure relief valve A.

Furthermore, a first relief outflow section 34 is formed in the small-diameter valve chamber 31 of the valve housing 3, at a suitable position between an intermediate position of the small-diameter valve chamber 31 in the axial direction, and the boundary with the large-diameter valve chamber 32. The first relief outflow section 34 is opened and closed by a reciprocal sliding movement of the small-diameter section 11 of the valve body 1, and when open, serves to expel oil to outside the valve housing 3 and return the oil to the inlet side of the oil pump 9, or to the oil pan 101. The oil-pressure relief valve A is not limited to the configuration described above, and may have any configuration, provided that the valve operates by detecting the pressure of the oil.

Furthermore, two first relief outflow sections 34 may be provided. In this case, the two first relief outflow sections 34 are disposed at a prescribed interval apart in the direction of movement of the valve body 1. By providing two first relief outflow sections 34, more detailed control of the oil pressure becomes possible.

The temperature-sensitive relief valve B is configured by a temperature-sensitive valve body 4 and a temperature-sensitive housing 5. The temperature-sensitive valve body 4 is configured by a temperature-sensitive valve section 41 and a temperature-sensitive drive section 42, and the temperature-sensitive drive section 42 detects the temperature of the oil and causes the temperature-sensitive valve section 41 to perform a sliding movement inside the temperature-sensitive housing 5. A second relief inflow section 51 and a second relief outflow section 52 are formed in the temperature-sensitive housing 5.

In this respect, a temperature-sensitive relief valve provided with a conventional temperature sensor is designed by aiming at a temperature change of approximately 5° C. to 10° C. in the oil temperature between the start and the end of operation. However, the temperature-sensitive relief valve B according to the present invention exhibits a larger temperature differential from the start to the end of the operation for performing relief of the oil, and more specifically, starts operation at approximately 50° C. (approximately 40° C. where necessary), and ends operation at approximately 120° C. (approximately 140° C. where necessary), and hence this oil temperature differential is approximately 70° C. (or approximately 100° C.)

In this way, the temperature range in which an oil relieving operation is performed by the temperature-sensitive relief valve B according to the present invention is expanded greatly compared to the prior art. It is also possible for the temperature-sensitive valve section 41 to move gradually from the start end to the finish end in the direction of movement, as the oil temperature changes from a low temperature to a high temperature. In other words, it is possible to implement control which progressively follows the oil temperature, within a broad oil temperature range, rather than on/off control as in the prior art.

The temperature-sensitive drive section 42 serves as a temperature sensor. More specifically, the temperature-sensitive drive section is a cylinder-type member and is configured by a cylinder 42 a and a piston 42 b. A temperature sensor 42 c is provided in the cylinder 42 a. A thermowax is used for the temperature sensor 42 c. More specifically, a portion which is filled with thermowax is provided in the cylinder 42 a (see FIG. 1), the thermowax expands and contracts thermally in accordance with the temperature detected thereby, and the piston 42 b extends or contracts with respect to the cylinder 42 a, accordingly.

By adopting a configuration in which a thermowax is used in the temperature sensor 42 c, it is possible to make, the device inexpensive. Furthermore, since the thermowax expands and contracts in a substantially accurate fashion, then the temperature-sensitive valve body 4 can operate more smoothly.

As described above, in the temperature-sensitive relief valve B, it is possible to implement control which progressively follows the oil temperature, within a broad oil temperature range, rather than on/off control as in the prior art. In the temperature-sensitive valve body 4 of the temperature-sensitive relief valve B, the amount of expansion/contraction changes gradually with change in the oil temperature. In other words, the temperature-sensitive valve body 4 closes so as to make the opening between the second relief inflow section 51 and the second relief outflow section 52 gradually become narrower, as the oil temperature rises, and is configured so as to be able to gradually reduce the amount of oil flowing via the second relief inflow section 51 and the second relief outflow section 52.

Furthermore, when the oil temperature falls, the temperature-sensitive valve body 4 opens in such a manner that the opening surface area gradually increases from a fully closed state between the second relief inflow section 51 and the second relief outflow section 52, whereby the amount of relieved oil can be increased gradually. More specifically, the temperature-sensitive drive section 42 which controls the operation of the temperature-sensitive valve body 4 does not have a structure in which the second relief inflow section 51 and the second relief outflow section 52 simply adopt either a fully open state or a fully closed state, depending on the oil temperature.

In the present invention, a configuration is adopted which enables the second relief inflow section 51 and the second relief outflow section 52 to be set to a state between open and closed, in addition to a fully closed and a fully open state. In other words, the temperature-sensitive valve body 4 can adjust the opening surface area between the second relief inflow section 51 and the second relief outflow section 52, in an optimal fashion in accordance with the temperature of the oil.

By means of a structure of this kind, the temperature-sensitive valve section 41 performs reciprocal movement inside the temperature-sensitive housing 5, with change in the oil temperature. In this case, when the oil temperature is low, the second relief inflow section 51 and the second relief outflow section 52 are fully open, and the amount of relieved oil passing through the temperature-sensitive relief valve B is set to a maximum. Furthermore, when the oil temperature is high, the second relief inflow section 51 and the second relief outflow section 52 are fully closed, and no oil is relieved via the temperature-sensitive relief valve B.

When the oil temperature is medium, the opening surface area between the second relief inflow section 51 and the second relief outflow section 52 is set to be slightly lower than a fully open state, near a low temperature within the medium temperature range. Furthermore, in the region near a high temperature in the medium temperature range, the second relief inflow section 51 and the second relief outflow section 52 are not fully closed, but rather opened with a small opening surface area.

In other words, when the temperature is medium but near a low temperature, then the amount of relieved oil can be set to a larger amount, whereas when the temperature is medium but near a high temperature, the amount of relieved oil can be set to a smaller amount. In this way, a structure is achieved in which, when the oil temperature is medium, the amount of relieved oil can be adjusted more or less steplessly.

A thermowax is used as the temperature-sensitive sensor 42 c in the temperature-sensitive drive section 42, but the temperature-sensitive drive section 42 is not limited to this, for example, a shape memory alloy, bimetal, or the like, may be used. The thermowax, shape memory alloy, bimetal, or the like, which is used in the temperature-sensitive drive section 42 does not employ an electrical system of any kind, and therefore in the present invention, this is called a “non-electronic control component”. By using a non-electronic control component in the temperature-sensitive drive section 42 of the temperature-sensitive relief valve B, since no electronically controlled components are used, then it is possible to achieve stable operation without being affected by problems in the electrical system.

Furthermore, the temperature-sensitive valve section 41 is provided with a supplementary elastic member 43, such as a coil spring, which applies a load in the opposite direction to the load of the recovery side drive section 42, in a direction which sets the second relief inflow section 51 and the second relief outflow section 52 to a communicating state at all times.

As described above, by using a non-electronic control component in the temperature sensor 42 c of the temperature-sensitive relief valve B, since no electronically controlled components are used, then it is possible to achieve stable operation without being affected by problems in the electrical system.

The oil pump 9 is an inscribing gear pump, which is configured by a pump housing 91, an inner rotor 95 and an outer rotor 96. A rotor chamber 92 is formed inside the pump housing 91, and an intake port 93 and a discharge port 94 are formed. In the pump housing 91, the side where the intake port 93 is formed is called an intake section 9A, and the side where the discharge port 94 is formed is called a discharge section 9B. A configuration including an intake opening, etc. of the intake port 93 is provided with the intake port 93 in the intake section 9A, and a configuration including a discharge opening, etc. of the discharge port 94 is provided with the discharge port 94 in the discharge section 9B.

The inner rotor 95 and the outer rotor 96 are disposed in the rotor chamber 92. External teeth are formed on the inner rotor 95, and internal teeth are formed on the outer rotor 96; the inner rotor 95 is disposed inside the outer rotor 96, the inner rotor 95 is driven and rotates together with the outer rotor 96, and oil taken in from the intake port 93 is discharged from the discharge port 94.

The oil pump 9 is incorporated into the oil circulation circuit 6. The oil circulation circuit 6 supplies lubricating oil to the engine E of an automobile, or the like, by the oil pump 9. The flow passage from the discharge section 9B of the oil pump 9 to the engine E in the oil circulation circuit 6 is called the upstream flow passage 61, and the flow passage from the engine E to the intake section 9A of the oil pump 9 is called the downstream flow passage 62. Furthermore, there is also a configuration wherein the oil pan 101 is provided inside the downstream flow passage 62, and the discharge section 9B communicates with the intake section 9A of the oil pump 9 via the oil pan 101.

Moreover, an oil filter 102 is provided in the upstream flow passage 61. The position where the oil filter 102 is disposed in the upstream flow passage 61 is a position whereby the temperature-sensitive relief valve B is to the upstream side of the oil filter 102 at all times. In other words, the temperature-sensitive relief valve B is provided to the upstream side of the oil filter 102. A relief flow passage 7 is provided between the oil pump 9 and the engine E, in other words, between an intermediate position of the upstream flow passage 61 of the oil circulation circuit 6, and the intake section 9A of the oil pump 9. The oil-pressure relief valve A and the temperature-sensitive relief valve B are provided in parallel, in the relief flow passage 7.

There are two embodiments for the configuration of the relief flow passage 7, and in the first embodiment, the relief flow passage 7 is divided into a first relief branch flow passage 71 which branches from the upstream flow passage 61 via a first branch section 7 a at a position near the oil pump 9, and a second relief branch flow passage 72 which branches via a second branch section 7 b at a position near the engine E (see FIG. 1).

Hence, the first relief branch flow passage 71 and the second relief branch flow passage 72 server as parallel flow passages, and the oil-pressure relief valve A is provided in the first relief branch flow passage 71 and the temperature-sensitive relief valve B is provided in the second relief branch flow passage 72, and by adopting a configuration of this kind, the oil-pressure relief valve A and the temperature-sensitive relief valve B are arranged in parallel.

The flow passage on the upstream side of the position where the oil-pressure relief valve A is provided in the first relief branch flow passage 71 is called the first upstream branch flow passage 71 a of the first relief branch flow passage 71, and the flow passage on the downstream side is called the first downstream branch flow passage 71 b. The first relief inflow section 33 of the oil-pressure relief valve A and the first upstream branch flow passage 71 a are connected, and the first relief outflow section 34 and the first downstream branch flow passage 71 b are connected (see FIG. 1).

Similarly, the flow passage on the upstream side of the position where the temperature-sensitive relief valve B is provided in the second relief branch flow passage 72 is called the second upstream branch flow passage 72 a of the second relief branch flow passage 72, and the flow passage on the downstream side is called the second downstream branch flow passage 72 b. The second relief inflow section 51 of the temperature-sensitive relief valve B and the second upstream branch flow passage 72 a are connected, and the second relief outflow section 52 and the second downstream branch flow passage 72 b are connected (see FIG. 1).

Furthermore, the oil filter 102 is positioned to the downstream side of the second branch section 7 b in the upstream flow passage 61 (see FIG. 1). In other words, as stated previously, the temperature-sensitive relief valve B is positioned to the upstream side of the oil filter 102. The first relief branch flow passage 71 and the second relief branch flow passage 72 can both send oil towards the intake section 9A of the oil pump 9 via the oil pan 101.

Moreover, in a second embodiment of the relief flow passage 7, one upstream shared flow passage 73 which is connected to the intake section 9A of the oil pump 9 via an intermediate position in the upstream flow passage 61 of the oil circulation circuit 6 is provided, an upstream two-leg branch section′7 c is provided at the end of the upstream shared flow passage 73, and the first relief branch flow passage 71 and the second relief branch flow passage 72 are provided in a parallel arrangement bifurcated from the upstream two-leg branch section 7 c (see FIG. 8).

The oil-pressure relief valve A is provided on the side of one of the first relief branch flow passage 71 and the second relief branch flow passage 72, and the temperature-sensitive relief valve B is provided on the other thereof. A downstream two-leg branch merging section 7 d is provided in the downstream end portion of the first relief branch flow passage 71 and the second relief branch flow passage 72, and a downstream shared flow passage 74 is provided from the downstream two-leg merging section 7 d. The downstream shared flow passage 74 communicates with the intake section 9A of the oil pump 9 via the oil pan 101.

In this way, in the second embodiment of the relief flow passage 7, the first relief branch flow passage 71 and the second relief branch flow passage 72 are provided in a two-legged shape between the upstream side end and the downstream side end, and the oil-pressure relief valve A and the temperature-sensitive relief valve B are disposed therein in a parallel arrangement. In this second embodiment as well, the oil filter 102 is provided in the upstream flow passage 61. The portion where the upstream shared flow passage 73 branches from the upstream flow passage 61 is called the upstream branch section 7 e, which is on the downstream of the oil filter 102.

The oil filter 102 is positioned on the downstream side of the upstream branch section 7 e (see FIG. 8). More specifically, the upstream branch section 7 e is located on the upstream side of the oil filter 102. Therefore, the temperature-sensitive relief valve B is constituted to be on the upstream side of the oil filter 102. The first relief branch flow passage 71 and the second relief branch flow passage 72 are configured to be able to send oil via the oil pan 101 to the side of the intake section 9A of the oil pump 9.

In the upstream flow passage 61 of the oil circulation circuit 6 according to the first embodiment, desirably, the oil-pressure relief valve A is provided in a position nearer to the side of the oil pump 9, and the temperature-sensitive relief valve B is provided nearer to the side of the engine E, and in particular, at a position directly next to or directly before the upstream side of the main gallery of the engine E. Therefore, control of the temperature-sensitive relief valve B can be implemented at an oil temperature, which is close to the oil temperature in the main gallery of the engine E, leading to accurate temperature control.

Although not illustrated in particular, the engine E includes a cylinder head and a cylinder block, and a main gallery (in other words, an oil passage provided inside the engine E), which is the furthest downstream portion of the upstream flow passage 61, is formed inside the cylinder block.

The temperature-sensitive relief valve B may be incorporated inside the cylinder block so as to have an integrated structure with the engine E, and the oil-pressure relief valve A may be incorporated into the pump housing 91 and have an integrated structure with the oil pump 9. Even in the case of a configuration of this kind, the oil-pressure relief valve A and the temperature-sensitive relief valve B are arranged in parallel in the relief flow passage 7.

The basic flow of oil in the oil circulation circuit 6 is now described. The oil discharged from the discharge section 9B side of the oil pump 9 flows to the oil circulation circuit 6, and oil is supplied to the engine E for lubrication and cooling, via the upstream flow passage 61. Thereupon, the oil which has been circulated through the engine E flows into the downstream flow passage 62 and returns again to the intake section 9A side of the oil pump 9. In this case, when the oil pan 101 is provided between the downstream flow passage 62 and the intake section 9A of the oil pump 9, then the oil collects in the oil pan 101 (see FIG. 1).

Next, a relief operation performed by the relief device according to the present invention will be described. As stated previously, the oil-pressure relief valve A and the temperature-sensitive relief valve B are disposed in parallel arrangement in the relief flow passage 7 where oil is relieved, and a relief operation is performed independently by these valves. The oil-pressure relief valve A and the temperature-sensitive relief valve B each operate individually in accordance with increase in the oil discharge pressure from the oil pump 9, or the oil temperature.

Below, an oil relieving operation is described in respect of the following case, in accordance with the oil temperature and the number of revolutions of the engine E. Here, the oil temperature is low when the temperature is approximately 50° C. or lower, and this low oil temperature has a temperature range from approximately 40° C. to less than approximately 60° C. Furthermore, a medium oil temperature is in a range from approximately 40° C. to approximately 130° C., but in the present invention, is a range from approximately 50° C. to approximately 120° C. Moreover, a high oil temperature is equal to or greater than approximately 120° C. Furthermore, in FIG. 1 to FIG. 8, the arrows marked along the oil circulation circuit 6 and the relief flow passage 7 indicate the flow and direction of oil.

When the oil temperature is low and the number of revolutions of the engine E is low, then the relief operation of the oil is as follows (see FIG. 2). The temperature-sensitive relief valve B relieves oil and the oil-pressure relief valve A does not relieve oil. A concrete example of circumstances of this kind is a situation immediately after starting the engine E, for example, when the oil has not warmed up sufficiently. Consequently, the oil temperature is low and the viscosity of the oil is high.

Since the oil pressure is low, then a relief operation is not performed by the oil-pressure relief valve A. On the other hand, in the temperature-sensitive relief valve B, when the oil temperature is low, the valve body 4 is in an open state so as to connect the second relief inflow section 51 and the second relief outflow section 52 with each other, and oil flows in the second relief branch flow passage 72 and is relieved.

When the oil temperature is low and the number of revolutions of the engine E is medium or high, then the relief operation of the oil is as follows (see FIG. 3). The temperature-sensitive relief valve B and the oil-pressure relief valve A both perform relief. In other words, when the number of revolutions of the engine E is medium or high, then the pressure of the oil becomes high, and therefore the oil-pressure relief valve A operates and oil is relieved on the basis of the oil pressure.

When the oil temperature is medium and the number of revolutions of the engine E is low, then the relief operation of the oil is as follows (see FIGS. 4A and 4B). The temperature-sensitive relief valve B relieves oil in such a manner that the amount of oil relieved becomes greater at a temperature nearer to a low temperature in the medium temperature range (see FIG. 4A). Furthermore, the amount of communication between the second relief inflow section 51 and the second relief outflow section 52 is reduced in such a manner that the amount of oil relieved becomes smaller at a temperature nearer to a high temperature within the medium temperature range. The oil-pressure relief valve A does not relieve oil since the number of revolutions of the engine E is low and as a result the oil pressure is low (see FIG. 4B).

When the oil temperature is medium and the number of revolutions of the engine E is medium or high, then the relief operation of the oil is as follows (see FIGS. 5A and 5B). The temperature-sensitive relief valve B relieves oil in such a manner that the amount of relieved oil becomes greater at a temperature nearer to a low temperature in the medium temperature range (see FIG. 5A). Moreover, oil is relieved in such a manner that the amount of relieved oil becomes smaller nearer to a high oil temperature within the medium oil temperature range. The oil-pressure relief valve A relieves oil since the oil pressure also rises when the number of revolutions of the engine E is medium and high (see FIG. 5B).

When the oil temperature is high and the number of revolutions of the engine E is low, then the oil relieving operation is as follows (see FIG. 6). At a high oil temperature, the temperature-sensitive relief valve B becomes fully closed, and does not relieve oil. Furthermore, the oil-pressure relief valve A does not relieve oil since the number of revolutions of the engine E is low and as a result the oil pressure is low.

When the oil temperature is high and the number of revolutions of the engine E is medium or high, then the relief operation of the oil is as follows (see FIG. 7). At a high oil temperature, the temperature-sensitive relief valve B becomes fully closed, and does not relieve oil. Furthermore, since the discharge pressure from the oil pump 9 is high, then the oil-pressure relief valve A does not relieve oil.

As described above, with the relief device according to the present invention, oil is relieved appropriately in accordance with the low temperature, medium temperature and high temperature of the oil, and the low number of revolutions, medium number of revolutions and high number of revolutions of the engine E. Consequently, as indicated by the graph (see FIG. 9) which indicates the oil pressure characteristics of the present invention, the oil pressure characteristics can be set to low oil pressure characteristics equivalent to those when the oil temperature is high, even when the oil temperature is low or medium.

Below, the main configuration of the present invention is described. The relief flow passage 7 is provided in such a manner that the first relief branch flow passage 71 and the second relief branch flow passage 72 are in a parallel arrangement, and the oil-pressure relief valve A is provided in the first relief branch flow passage 71 and the temperature-sensitive relief valve B is provided in the second relief branch flow passage 72. The sensor which detects the temperature of the temperature-sensitive relief valve B (temperature-sensitive sensor 42 c) uses a non-electronic component. Moreover, in the temperature-sensitive relief valve B, the operation of the temperature-sensitive valve body 4 which moves by detecting the oil temperature is a smooth and gradual movement with respect to change in the oil temperature.

In the relief device according to the present invention, as described above, when the oil temperature is low, the temperature-sensitive relief valve B relieves oil, when the oil temperature is medium, the temperature-sensitive relief valve B relieves a large amount of oil at a temperature nearer to a low temperature, and relieves a small amount of oil at a temperature nearer to a high temperature, and when the oil temperature is high, the temperature-sensitive relief valve B does not relieve oil.

Furthermore, in the embodiment of the present invention, the oil pump 9 is an inscribing gear pump, but the pump is not limited to this, and an external gear pump, vane pump, or the like, may be used. In other words, provided that the pump is an oil pressure generation source, the type of pump is immaterial.

Moreover, in the embodiment of the present invention, in order to make the control by the temperature sensor 42 c more accurate, and to improve the response, the temperature sensor 42 c may be disposed adjacently to the upstream flow passage 61, or partially projecting into same. Furthermore, in the second embodiment of the present invention, the number of components is reduced by adopting a structure in which the valve housing 3 and the temperature-sensitive housing 5 are formed in an integrated fashion by casting, or the like.

In the present invention, as stated previously, since a configuration is adopted in which an oil filter 102 is provided in the upstream flow passage 61 of the oil circulation circuit 6, and furthermore the temperature-sensitive relief valve B is positioned to the upstream side of the oil filter 102, then the temperature-sensitive relief valve B can detect the discharge pressure of the oil pump 9 with high accuracy and control the relieving of oil.

The oil pressure loss caused by the oil, filter 10-2 varies with the temperature. The pressure loss is the amount of decrease in the oil pressure. Therefore, when the temperature-sensitive relief valve B is positioned to the downstream side of the oil filter 102, then the oil pressure of the oil which has undergone pressure loss is controlled by the temperature-sensitive relief valve B, and change in the actual pressure of the oil discharged from the oil pump 9 becomes difficult to detect.

In the present invention, as reiterated, an oil filter 102 is provided in the upstream flow passage 61 of the oil circulation circuit 6, and the temperature-sensitive relief valve B is positioned to the upstream side of the oil filter 102. Therefore, it is possible to implement control by the temperature-sensitive relief valve B without being affected by pressure loss in the oil filter 102 which varies with the oil temperature.

Moreover, in the present invention, it is also possible to provide the oil filter 102 inside the pump housing 91, in a structure of the oil pump 9 in which the oil-pressure relief valve A and the temperature-sensitive relief valve B are incorporated as a unit inside the pump housing 91 of the oil pump 9. In this case, a portion of the upstream flow passage 61 of the oil circulation circuit 6 is provided inside the pump housing 91.

In the second embodiment, when the oil temperature is low, the oil is relieved from the temperature-sensitive relief valve also, and not only the oil-pressure relief valve. Therefore, when the oil temperature is low, which causes the oil pressure to rise, the oil is relieved at all times from the temperature-sensitive relief valve, regardless of whether or not oil is received by the oil-pressure relief valve. Due to the foregoing, the oil pressure is prevented from rising when the oil temperature is low, and therefore it is possible to prevent deterioration of fuel consumption at low temperature.

In the third embodiment, when the oil temperature is medium, the amount of oil relieved by the temperature-sensitive relief valve becomes greater near a low temperature, and becomes smaller near a high temperature. A medium temperature is a temperature range between a low oil temperature and a high oil temperature. Accordingly, in the medium temperature range, there is a large temperature difference between the side near a low temperature and the side near a high temperature. Therefore, a large differential in the viscosity of the oil also occurs within the medium temperature range.

Consequently, when the oil temperature is medium, the viscosity of the oil is greater and the oil pressure increases, the lower the oil temperature, and the viscosity is smaller and the oil pressure decreases, the higher the oil temperature. Therefore, when the oil temperature is low within the medium temperature range, the temperature-sensitive relief valve implements control so as to increase the amount of relieved oil, and therefore, even if the oil temperature falls, the oil pressure does not rise and the discharge pressure can be maintained at a substantially uniform low oil pressure, thus avoiding decline in the fuel consumption.

In the fourth embodiment, a configuration is adopted wherein, when the oil temperature is high, the temperature-sensitive relief valve does not relieve oil. Therefore, it is possible to promote cooling and/or lubrication. In the fifth embodiment, by adopting a configuration wherein the temperature-sensitive relief valve is provided in the engine, since the temperature-sensitive relief valve is to the upstream side of the main gallery, which is an oil passage disposed inside the cylinder block, and is installed in the cylinder block of the engine, then the cylinder block of the engine can also serve as the housing of the temperature-sensitive relief valve, without the need to prepare a special valve housing for the temperature-sensitive relief valve, and it is possible to reduce the size of the device and the number of components.

In the sixth embodiment, by adopting a configuration in which the relief flow passage branches from the upstream flow passage, the oil-pressure relief valve and the temperature-sensitive relief valve are provided in parallel in the relief flow passage, and the branch section of the relief flow passage is positioned to the upstream side of the oil filter, then it is possible to dispose the temperature-sensitive relief valve to the upstream side of the oil filter in the upstream flow passage, and the temperature-sensitive relief valve can control the relieving of oil with sufficiently high accuracy, without being affected by differences in the pressure loss in the oil filter due to differences in the oil temperature. 

1. A relief device for an oil circuit of an engine, the device comprising: an oil pump; an upstream flow passage provided from a discharge section side of the oil pump to an engine; an oil-pressure relief valve which relieves oil by a valve body moving due to oil pressure; and a temperature-sensitive relief valve which relieves oil by detecting an oil temperature and opening and closing steplessly, wherein the oil-pressure relief valve and the temperature-sensitive relief valve are disposed in parallel arrangement in the upstream flow passage, an oil filter is provided in the upstream flow passage, and the temperature-sensitive relief valve is positioned on the upstream side of the oil filter.
 2. The relief device for an oil circuit of an engine according to claim 1, wherein, when the oil temperature is low, the temperature-sensitive relief valve relieves oil.
 3. The relief device for an oil circuit of an engine according to claim 1, wherein, when the oil temperature is medium, the amount of oil relieved by the temperature-sensitive relief valve becomes greater near a low oil temperature, and becomes smaller near a high oil temperature.
 4. The relief device for an oil circuit of an engine according to claim 1, wherein, when the oil temperature is high, the temperature-sensitive relief valve does not relieve oil.
 5. The relief device for an oil circuit of an engine according to claim 1, wherein the temperature-sensitive relief valve is provided in the engine.
 6. The relief device for an oil circuit of an engine according to claim 1, wherein a relief flow passage branches from the upstream flow passage, the oil-pressure relief valve and the temperature-sensitive relief valve are provided in a parallel arrangement in the relief flow passage, and the branch section of the relief flow passage is positioned on the upstream side of the oil filter. 